1. Technical Field
The present invention relates to an engine control device that controls a turbocharged engine and auxiliaries thereof, and in particular to an engine control device capable of suppressing a flow rate of purge gas even when a purge valve provided in a pipe line is stuck open, the pipe line suctioning the purge gas from a canister by an ejector.
2. Related Art
An evaporated fuel processing device is provided in an automobile on which a gasoline engine is mounted, and prevents discharge of evaporated fuel gas (fuel vapor) generated in a fuel tank to outside.
In the evaporated fuel processing device, activated charcoal in a canister adsorbs and temporarily stores the evaporated fuel gas. When an engine is driven, the evaporated fuel gas is introduced from the canister into an intake system and is subjected to combustion processing in a combustion chamber. In this way, the evaporated fuel gas is purged from the canister.
In general, the evaporated fuel gas (purge gas) is introduced from the canister into the intake system by using negative pressure of an intake pipe when the engine is driven.
As related art on the evaporated fuel processing device, for instance, Japanese Unexamined Patent Application Publication (JP-A) No. 2013-174143 describes that, in order to allow canister purge in a turbocharged engine during turbocharging, an ejector as a type of a negative pressure generator is provided in a passage that bypasses an upstream side and a downstream side of a compressor, and suctions the purge gas.
As related art on such a bypass passage, it is described in Japanese Unexamined Patent Application Publication (JP-A) No. 62-78430 that an air-bypass valve is provided in the passage that bypasses the upstream side and the downstream side of the compressor, and can open/close the passage.
In addition, as related art on diagnosis, fail-safe, and the like during malfunction of a purge valve, it is described in Japanese Unexamined Patent Application Publication (JP-A) No. 8-14117 that purge valve open malfunction is determined on the basis of output of an air-fuel ratio sensor that is output after a close operation signal is output in an opened state of the purge valve and that a drain cut valve and a tank pressure valve are closed in accordance with a positive determination.
It is described in Japanese Unexamined Patent Application Publication (JP-A) No. 8-326611 that a ventilation blocking valve is provided in a ventilation pipe that communicates between the canister and ambient air and that the ventilation blocking valve is closed when open malfunction of a purge control valve is detected.
The ejector that suctions the purge gas by using differential pressure between an input side and an output side of the compressor of a turbocharger is provided. In this way, the canister purge can be performed in a supercharging region where the negative pressure of the intake pipe is not generated.
In a so-called downsized turbo engine with a relatively high use frequency of the supercharging region, such an ejector is effective in securing a sufficient canister purge ability.
However, when stuck open malfunction occurs to the purge valve in the engine having such an ejector, a flow rate of the purge gas can no longer be controlled, and an excess amount of the purge gas is introduced into the intake pipe line. Consequently, an air-fuel ratio becomes excessively rich, which possibly leads to degraded drivability (ease of driving) and an engine stall due to rich misfire.